In a conventional vehicle steer axle assembly, a steering knuckle includes a body, steering arms, a brake mounting plate, and a spindle for a wheel hub, bearings, and a tire assembly (see, for example, U.S. Pat. No. 6,623,019 which is incorporated herein by reference). The steering knuckle is coupled to a steer axle using a separable kingpin and the steering arms are connected to steering components of a vehicle.
Typically, the steering knuckle has a forked yoke that defines first and second bosses with aligned bores. The yoke surrounds one end of the steer axle which defines an axle boss having an axle bore aligned with the bores of the knuckle yoke. The kingpin extends through one or more of the knuckle bores, through the axle bore, and through the remaining knuckle bore to rotatably couple the steering knuckle and the steer axle together.
In these conventional steer axle assemblies, the knuckle pivots about the kingpin on a vertically inclined steering axis. Typically, bushings are disposed (for example, pressed) within the aligned bores of the knuckle to allow the knuckle to rotate relative to the kingpin.
Conventional steer axle assemblies suffer from several disadvantages. Typically, conventional steer axle assemblies allow a relatively large amount of axial and radial movement of the knuckle relative to the kingpin, which results in the kingpin joints being subjected to added wear. As a result, greater clearances are created, which permit the kingpin to shift and oscillate within the knuckle bores which reduces the useful lives of the assembly components.
Conventional kingpin designs also often require manual shimming of steer axle assembly members in order to limit the above stated axial and radial movement of the knuckle relative to the kingpin. Therefore, these designs require additional manufacturing steps and costs. Typically, the bushings result in relatively large tolerances and often require the operations of broaching or reaming of the bushings. These operations may be required to maintain close fit tolerances of the inside diameter of the bushing to the outside diameter of the kingpin.
Knuckles, such as those described above are complex and, thus result in high material, manufacturing, and labor costs. These knuckles are also disadvantageous since the kingpin can be difficult to remove for repairs and the kingpin itself increases the size and weight of the steer axle assembly. Further, the kingpin to steer axle joint is highly loaded and, consequently, requires a precision fit tolerance and a robust mechanism to lock the kingpin to the axle beam. The localized stress at this joint also typically requires that high strength materials be used for the kingpin.
What is sought is to provide vehicle steer axle assemblies that do not utilize a separable kingpin, wherein the joint(s) between the steer axle and the steering knuckle is eliminated. This should at least result in providing vehicle steer axle assemblies with lower material and labor costs, with an elimination of endplay, with a lowering of mechanical stress in the coupling area, and with an elimination of manual shimming.